EP0024707B1 - Electromagnetic ultrasonic apparatus - Google Patents

Electromagnetic ultrasonic apparatus Download PDF

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Publication number
EP0024707B1
EP0024707B1 EP80105010A EP80105010A EP0024707B1 EP 0024707 B1 EP0024707 B1 EP 0024707B1 EP 80105010 A EP80105010 A EP 80105010A EP 80105010 A EP80105010 A EP 80105010A EP 0024707 B1 EP0024707 B1 EP 0024707B1
Authority
EP
European Patent Office
Prior art keywords
magnetic pole
pole piece
transmitting
coils
end surface
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80105010A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0024707A3 (en
EP0024707A2 (en
Inventor
Ichiya Sato
Kazuo Miyagawa
Yukihito Sasaki
Kohji Kawamura
Shuichi Sato
Sohji Sasaki
Jun Kubota
Susumu Ito
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Nippon Steel Corp
Original Assignee
Hitachi Ltd
Nippon Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd, Nippon Steel Corp filed Critical Hitachi Ltd
Publication of EP0024707A2 publication Critical patent/EP0024707A2/en
Publication of EP0024707A3 publication Critical patent/EP0024707A3/en
Application granted granted Critical
Publication of EP0024707B1 publication Critical patent/EP0024707B1/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/04—Sound-producing devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02854—Length, thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0421—Longitudinal waves

Definitions

  • the present invention relates to an electromagnetic ultrasonic apparatus and more particularly, to an electromagnetic ultrasonic apparatus which permits examining the quality of conductive materials, for example, metal strips, ingots and bullet type steel and aluminum without being brought into contact therewith.
  • An electromagnetic ultrasonic apparatus permits transmitting and receiving ultrasonic waves as it is in a non-contact state, and is useful as an instrument for examining materials, without destroying the same, for example, moving materials, and materials which are difficult to contact physically due to the temperature or shape thereof.
  • An electromagnetic ultrasonic apparatus comprising a transmitting magnetic pole piece provided such that the front end surface of the transmitting magnetic pole piece can be brought close and in opposition to one surface of a material to be examined, a receiving magnetic pole piece which is provided such that the front end surface of the receiving magnetic pole piece can be brought close and in opposition to the opposite surface of the material and which has a magnetic polarity opposite to that of the transmitting magnetic pole piece, an exciter coil for supplying a DC magnetic field to the transmitting and receiving magnetic pole pieces and transmitting and receiving coils provided at the front end surfaces of the transmitting and receiving magnetic pole pieces is described in, for example, "British Journal of NDT", July 1977, pages 178-184, G.J. Parkinson and D. M. Wilson.
  • each of the transmitting and receiving coils is formed as one dual spiral coil to have a constant wave front transmitted from, and received by, a circular central region of the respective coil.
  • each of the transmitting and receiving coils is formed as a rectangular coil, and GB-A-1 425 201, which uses flat transmitting and receiving coils, the shape of which is not disclosed in detail.
  • the transmitting and receiving coils are again each formed by one single coil.
  • the output voltages of receiving coils of an electromagnetic ultrasonic apparatus vary depending upon various electromagnetic conditions, for example, magnetic flux density B, air gap G between transmitting and receiving coils and the surfaces of the material being examined, and specific permeability ju., of the material.
  • magnetic flux density B for example, magnetic flux density B
  • air gap G between transmitting and receiving coils and the surfaces of a material being examined is varied by 1 mm
  • specific permeability ju. of the material.
  • the output voltages of the receiving coils are varied by approximately 6 dB.
  • JP-Al-86388/1977 shows that when two electromagnetic ultrasonic apparatus are arranged close to each other to utilize the difference between the output voltages occurring in the two receiving coils, the mode conversion echo and external noise deaden each other.
  • the difference between the waves passing through the material being examined and the back face echo can be obtained as an output from the receiving coils, so that the capability of this apparatus to detect flaws in the material is improved to a certain extent.
  • the end surfaces of the transmitting and receiving magnetic pole pieces are each divided so as to provide separate pole surfaces.
  • the output signals of the receiving coils vary quite considerably in dependency on even subtle changes of various electromagnetic conditions. The disposition of the receiving coils on separate magnetic pole pieces in this known apparatus does not permit the required adjustment of these conditions.
  • two sets of transmitting coils and receiving coils are provided at the front end surface of one transmitting magnetic pole piece and one receiving magnetic pole piece, respectively, it is possible to arrange the transmitting coils and receiving coils such that they are spaced from each other by not more than 1 cm. As a result, the electromagnetic conditions for two sets of transmitting coils and receiving coils resemble each other. This allows the flaw detecting capability of the electromagnetic ultrasonic apparatus to be further improved.
  • magnetic pole pieces 10, 12 have end surfaces 16, 18, respectively, which are close and in opposition to a conductive material 14 to be examined.
  • the material 14 consists of, for example, a hot strip being subjected to a rolling step.
  • Magnetic members 20, 22, which constitute the magnetic pole pieces 10, 12, respectively, have cassette holding bores 24, 26 in the central portions thereof, and are kept spaced from the material 14 by a predetermined distance by means of wheels 28, 30 which are in contact with the material 14.
  • the wheels 28, 30 are rotatably supported on the side surfaces of the magnetic members 20, 22 via shafts 32, 34.
  • Cassettes 40, 42, to the ends of which transmitting coils 36, 37, and receiving coils 38, 39 are attached (see Fig. 2), respectively, are inserted into the cassette holding bores 24, 26 to be secured to the members 20, 22 with screws 44, 46.
  • the cassette 40 is provided on its lower end surface with a ceramic coil retainer 54 having a thermal resistance, and the transmitting coils 36, 37 are formed at the inner side of the coil retainer 54 by a printing wiring technique.
  • the transmitting coils 36, 37 are provided close to each other in the same plane which is in the magnetic field of the magnetic pole piece 10 and which is parallel to the end surface 16 thereof, and cumulatively connected to each other.
  • the cassette 42 is provided on its upper end surface with a material having a thermal resistance, for example, a ceramic coil retainer 56, and the receiving coils 38, 39 are formed at the inner side of the coil retainer 56 by a printing wiring technique.
  • the receiving coils 38, 39 are provided close to each other in the same plane which is in the magnetic field of the magnetic pole piece 12 and which is parallel to the end surface 18 thereof, and differentially connected to each other.
  • the transmitting and receiving coils 36, 37, 38, 39 are formed to selected dimensions; they have, for example, an outer diameter of 10 mm, an inner diameter of 0.8 mm and 15 turns of winding. These transmitting and receiving coils 36, 37; 38, 39 are provided in alignment and close to each other on the end surfaces 16, 18 of the magnetic pole pieces 10, 12 such that the distance between the center of coils is approximately 10 mm. Since the end surfaces 16, 18 of the magnetic pole pieces 10, 12 are kept spaced by a predetermined distance from the material to be examined, by means of the wheels 28, 30, the distance between the transmitting coils 36, 37 and the material 14 and the distance between the receiving coils 38, 39 and the material 14 are kept at a predetermined level, for example, 1.7 mm.
  • the transmitting and receiving coils 36, 37; 38, 39 are connected to a control circuit 62 via lead wires 58, 60, respectively.
  • the transmitting and receiving coils can be withdrawn with the cassettes 40, 42 from the magnetic members 20, 22 after the screws 44, 46 have been removed.
  • the magnetic pole pieces 10, 12 are fixed to a frame 74 which is secured to a support 72.
  • DC magnetic field generating means 76, 78 surrounding the magnetic pole pieces 10, 12 consists of coil bobbins 80, 82, insulating materials 84, 86, and DC exciter coils 88, 90.
  • the coil bobbins 80, 82 are fastened to the frame 74 with screws 92, 94.
  • the DC exciter coils 88, 90 are connected to a DC power source and generate in the magnetic pole pieces 10, 12 magnetic fields which cause the magnetic flux densities to be 2 teslas.
  • the transmitting coils 36, 37 are connected to a pulser 98 as shown in Fig. 4, which generates a pulser current lp.
  • the receiving coils 38, 39 are differentially connected to each other, and a node 100 thereof is grounded.
  • the remaining output terminals 102, 104 are connected to input terminals 108, 110 of a differential amplifier 106.
  • An output from the differential amplifier 106 is supplied to an observation unit, for example, a synchroscope 112 so as to be displayed in image.
  • An output from the differential amplifier 106 is also supplied to a signal controller 114 to be input into an automatic detector 116.
  • a gate amplifier 118 causes the output from the signal controller 114 to be supplied to the automatic detector 116 for a predetermined period of time, and actuate the detector 116 when the output from the signal controller 114 has exceeded a predetermined level.
  • eddy currents occur at the upper and lower surfaces of the material 14 due to high frequency magnetic field generated by the pulse current.
  • the eddy currents and DC magnetic field act on each other to generate stress waves (ultrasonic waves) in accordance with Fleming's left-hand rule.
  • the stress waves are propagated as oscillatory waves in the direction of the thickness of the material being examined, to reach the bottom surface thereof.
  • the waves which have reached the bottom surface of the material generate a high frequency magnetic field by an electromagnetic process opposite to the electromagnetic process by which the stress waves are generated.
  • the oscillatory stress waves and DC magnetic field act on each other at the bottom surface of the material, and an electric current in accordance with Fleming's right-hand rule flows to the lower surface of the material. Due to the magnetic field generated by this electric current, a voltage occurs in the receiving coils 38, 39.
  • the electromagnetic waves (transversal waves) generated by the transmitting coils 36, 37 directly reach the receiving coils 38, 39. Since reception outputs generated in the receiving coils 38, 39 are of substantially the same amplitude and waveform, a differential output (an output from the differential amplifier 106) is substantially zero.
  • a sending pulse T is supplied to the pulser 98, a first transmitted wave P, is received by the receiving coils 38, 39.
  • a mode conversion echo M 1 (longitudinal wave) is generated.
  • a mode conversion echo M 2 (longitudinal wave) is generated. Since the mode conversion echoes M 1 , M 2 advance at a high speed, they are received by the receiving coils 38, 39 at times shown in Figs. 6A and 6B.
  • an output from the differential amplifier 106 is as shown in Fig. 6C.
  • the transmitting coils 36, 37 and receiving coils 38, 39 in this embodiment are provided close to each other on the same end surfaces 16, 18 of the magnetic pole pieces 10, 12, respectively, so that gaps between the transmitting and receiving coils 36, 37; 38, 39 and the material 14 are kept substantially the same. Also, when the material 14 has no flaws, the output from the differential amplifier 106, i.e. noises, is kept low. When the material has a flaw F just above the receiving coil 38 as shown in Fig.
  • the signal control circuit 114 is adapted to set a gate width and a threshold level in accordance with the purpose of measurement to actuate the automatic detector 116.
  • a gate amplifier 118 causes the output from the signal control circuit 114 to be input into the detector 116 for only such a period of time that a first transmitted wave P, is generated. (The length of the time is set in accordance with the thickness of the material to be examined.) Therefore, the first transmitted wave P, only is input into the detector 116. When such an input into the detector 116 has exceeded a threshold level, for example, 6 dB, an output is generated therein to indicate the existence of a flaw in the material or give warning.
  • a threshold level for example, 6 dB
  • Fig. 8 is a graphical diagram showing the flaw detection characteristics of the above- described embodiment, wherein the gap between the end surfaces of the magnetic pole pieces and a material to be examined, and the magnetic flux density are set to 1.7 mm and 2 teslas, respectively. According to this embodiment, a flaw of 1 mm in diameter could be detected at a S/N ratio of approximately 9 dB.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
EP80105010A 1979-08-24 1980-08-22 Electromagnetic ultrasonic apparatus Expired EP0024707B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP107190/79 1979-08-24
JP10719079A JPS5631637A (en) 1979-08-24 1979-08-24 Instrument unit of electromagnetic ultrasonic wave

Publications (3)

Publication Number Publication Date
EP0024707A2 EP0024707A2 (en) 1981-03-11
EP0024707A3 EP0024707A3 (en) 1981-04-01
EP0024707B1 true EP0024707B1 (en) 1984-12-12

Family

ID=14452744

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80105010A Expired EP0024707B1 (en) 1979-08-24 1980-08-22 Electromagnetic ultrasonic apparatus

Country Status (4)

Country Link
US (1) US4348903A (ru)
EP (1) EP0024707B1 (ru)
JP (1) JPS5631637A (ru)
DE (1) DE3069797D1 (ru)

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57144456A (en) * 1981-03-02 1982-09-07 Hitachi Ltd Non-destructive inspecting device
DE3275315D1 (en) * 1981-06-10 1987-03-05 Hitachi Ltd Electromagnetic-acoustic measuring apparatus
JPS57208451A (en) * 1981-06-18 1982-12-21 Hitachi Ltd Electromagnetic type ultrasonic flaw inspector
JPS5841347A (ja) * 1981-09-04 1983-03-10 Hitachi Ltd 溶接部検出装置
US4449411A (en) * 1982-04-22 1984-05-22 Magnetic Analysis Corporation Magnetic and ultrasonic objects testing apparatus
US4449408A (en) * 1982-04-22 1984-05-22 Magnetic Analysis Corporation EMAT Test apparatus having retractable probe
US4523473A (en) * 1983-08-08 1985-06-18 The Charles Stark Draper Laboratory, Inc. Magneto-elastic material defect detector
DE3401072C2 (de) * 1984-01-13 1986-04-10 Nukem Gmbh, 6450 Hanau Elektrodynamischer Wandlerkopf
DE3413787A1 (de) * 1984-04-12 1985-10-17 Nukem Gmbh, 6450 Hanau Verfahren und vorrichtung zur pruefung von elektrisch leitenden gegenstaenden mittels ultraschall
JPS61245056A (ja) * 1985-04-22 1986-10-31 Mitsubishi Electric Corp 板波トランスデユ−サ
DE3530525C2 (de) * 1985-08-27 1994-05-11 Foerster Inst Dr Friedrich Vorrichtung zur zerstörungsfreien Werkstoffprüfung
DE3614069A1 (de) * 1986-04-24 1987-11-12 Mannesmann Ag Vorrichtung zur zerstoerungsfreien pruefung durch ultraschall
US5154081A (en) * 1989-07-21 1992-10-13 Iowa State University Research Foundation, Inc. Means and method for ultrasonic measurement of material properties
US5493511A (en) * 1992-12-08 1996-02-20 Administrator, National Aeronautics And Space Administration High speed thin plate fatigue crack monitor
CA2151116C (en) * 1994-06-09 1999-09-14 Paul J. Latimer Zig-zag electromagnetic acoustic transducer scan
US5714688A (en) * 1994-09-30 1998-02-03 The Babcock & Wilcox Company EMAT measurement of ductile cast iron nodularity
JPH08334431A (ja) * 1995-06-09 1996-12-17 Mitsubishi Electric Corp 非破壊検査装置
US10808756B2 (en) 2007-04-13 2020-10-20 Waukesha Bearings Corporation Compliant bearing
FI124803B (fi) * 2011-10-21 2015-01-30 Idsens Oy Menetelmä ja laitteisto kiinteiden esineiden vahvistamiseksi aidoksi
GB201419219D0 (en) * 2014-10-29 2014-12-10 Imp Innovations Ltd Electromagnetic accoustic transducer

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3469182A (en) * 1967-06-23 1969-09-23 Gkn Group Services Ltd Flaw detecting apparatus with mechanical scanning of detection means
US3583213A (en) * 1968-07-26 1971-06-08 James R Houck Nondestructive testing of conductive objects using ultrasonic waves
US3786672A (en) * 1972-09-20 1974-01-22 Atomic Energy Commission Two-dimensional coils for electro-magnetic generation and detection of acoustic waves
GB1425201A (en) * 1973-06-19 1976-02-18 British Steel Corp Ultrasonic testing of articles
FR2245251A5 (en) * 1973-09-25 1975-04-18 Inst Introskopii Non-destructive ultrasonic tester of workpieces - has electrically conductive surface for quality control and thickness measurement
JPS5286388A (en) * 1976-01-13 1977-07-18 Nippon Steel Corp Method of detecting flaw by supersonic waves
GB1565063A (en) * 1976-06-17 1980-04-16 Ti Ultrasound
DE2643601C3 (de) * 1976-09-28 1979-03-08 Hoesch Werke Ag, 4600 Dortmund Verfahren zur zerstörungsfreien Werkstoffprüfung mit Ultraschall unter Verwendung eines elektrodynamischen Schallwandlers
JPS53143388A (en) * 1977-05-20 1978-12-13 Nippon Steel Corp Ultrasonic wave reception of electromagnetic type

Also Published As

Publication number Publication date
EP0024707A3 (en) 1981-04-01
JPS5631637A (en) 1981-03-31
EP0024707A2 (en) 1981-03-11
JPS6323505B2 (ru) 1988-05-17
DE3069797D1 (en) 1985-01-24
US4348903A (en) 1982-09-14

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